import pygame
from pygame.sprite import Sprite


class Ship(Sprite):

    def __init__(self, ai_settings, screen):
        super(Ship, self).__init__()
        self.ai_settings = ai_settings
        """初始化飞船并设置其初始位置"""
        self.screen = screen
        # 加载飞船图像并获取其外接矩形
        self.image = pygame.image.load('ship.bmp')
        self.rect = self.image.get_rect()
        self.screen_rect = screen.get_rect()
        # 将每艘飞船放在屏幕底部中央
        self.rect.centerx = self.screen_rect.centerx
        self.rect.bottom = self.screen_rect.bottom
        # 移动标志
        self.moving_right = False
        self.moving_left = False

    def blit_me(self):
        """在指定位置绘制飞船"""
        self.screen.blit(self.image, self.rect)

    def update(self):
        if self.moving_right and self.rect.right < self.screen_rect.right:  # 右移
            self.rect.centerx += self.ai_settings.ship_speed_factor
        elif self.moving_left and self.rect.left > self.screen_rect.left:  # 左移
            self.rect.centerx -= self.ai_settings.ship_speed_factor

    def center_ship(self):
        """让飞船在屏幕居中"""
        self.rect.centerx = self.screen_rect.centerx
        self.rect.bottom = self.screen_rect.bottom
